Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
  • C08C19/00—Chemical modification of rubber
  • C08C19/30—Addition of a reagent which reacts with a hetero atom or a group containing hetero atoms of the macromolecule
  • C08C19/42—Addition of a reagent which reacts with a hetero atom or a group containing hetero atoms of the macromolecule reacting with metals or metal-containing groups
  • C08C19/44—Addition of a reagent which reacts with a hetero atom or a group containing hetero atoms of the macromolecule reacting with metals or metal-containing groups of polymers containing metal atoms exclusively at one or both ends of the skeleton
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
  • C08L9/06—Copolymers with styrene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/56—Organo-metallic compounds, i.e. organic compounds containing a metal-to-carbon bond
  • C08K5/57—Organo-tin compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L7/00—Compositions of natural rubber
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons

Definitions

• This invention relates to a rubber composition suitable for use in a tire tread having a low rolling resistance, a high wet skid resistance and an excellent processability.
• rubber blends of styrene-butadiene copolymer such as emulsion polymerized styrene-butadiene copolymer, solution polymerized styrene-butadiene copolymer or the like and polybutadiene such as high-cis polybutadiene, low-cis polybutadiene or the like have widely been used as a tire tread for passenger car.
• styrene-butadiene copolymer such as emulsion polymerized styrene-butadiene copolymer, solution polymerized styrene-butadiene copolymer or the like
• polybutadiene such as high-cis polybutadiene, low-cis polybutadiene or the like
• a rubber composition for use in tires comprising at least 20% by weight of a conjugated diolefin-vinyl-substituted aromatic hydrocarbon random copolymer based on the total weight of the rubber content, said random copolymer being produced by copolymerizing in the presence of an organolithium polyfunctional initiator or in the presence of an organomonolithium initiator and a polyfunctional monomer and then subjecting to a coupling reaction with a compound inclusive of a halogenated tin compound, and satisfying the following requirements:
• a content of vinyl-substituted aromatic hydrocarbon is 3 to 60% by weight
• a content of tin bonded to the copolymer is not less than 400 ppm
• a Mooney viscosity (iii) is 20 to 200.
• the conjugated diolefin-vinyl-substituted aromatic hydrocarbon random copolymer (hereinafter referred to as a conjugated diolefinic copolymer) used in the invention is produced by copolymerizing a conjugated diolefin and a vinyl-substituted aromatic hydrocarbon in the presence of a particular organolithium polymerization initiator, and has the content of vinyl-substituted aromatic hydrocarbon of 3-60% by weight, preferably 3-50% by weight.
• conjugated diolefin butadiene, isoprene and so on are preferably used.
• vinyl-substituted aromatic hydrocarbon styrene, ⁇ -methylstyrene, p-methylstyrene and the like are preferably used.
• the conjugated diolefinic copolymer used in the invention is subjected to a coupling reaction with a compound inclusive of a halogenated tin compound, so that the content of tin bonded to the copolymer is not less than 400 ppm, preferably not less than 500 ppm. Moreover, the upper limit of the tin content is 10,000 ppm because it is difficult to produce the conjugated diolefinic copolymer having the tin content of more than 10,000 ppm in industry.
• the content of tin bonded to the copolymer is measured as follows. That is, the resulting copolymer is again dissolved in toluene and poured into a large amount of methanol to remove the resulting precipitate of the unreacted tin compound from the copolymer. Thereafter, the amount of tin bonded to the copolymer is determined by atomic-absorption spectroscopy for the copolymer. When the tin content in the copolymer is less than 400 ppm, the rolling resistance becomes poor.
• the molecular weight distribution of the resulting conjugated diolefinic copolymer is broad and has Mw/Mn (ratio of weight average molecular weight to number average molecular weight measured by GPC) of not less than 2.
• Mw/Mn ratio of weight average molecular weight to number average molecular weight measured by GPC
• Mooney viscosity (ML 1+4 100 ° C.) of the conjugated diolefinic copolymer according to the invention is 20 to 200, preferably 30 to 150. When the Mooney viscosity is less than 20, the fracture properties and rolling resistance are poor, while when it exceeds 200, the processability is poor and also the industrial production is difficult.
• conjugated diolefinic copolymer according to the invention will be described below.
• This copolymer is produced by copolymerization in the presence of organolithium polyfunctional initiator or in the presence of organomonolithium initiator and polyfunctional monomer and then coupling with a compound inclusive of a halogenated tin compound.
• the copolymerization of conjugated diolefin and vinyl-substituted aromatic hydrocarbon is carried out in a solvent such as n-hexane, n-heptane, toluene, benzene, cyclohexane or the like in the presence of a particular organolithium initiator.
• organolithium polyfunctional initiators such as tetramethylene-1,4-dilithium, hexamethylene-1,6-dilithium, 1,3-dilithiobenzene, 1,4-dilithiobenzene, octamethylene-1,8-dilithium, 1,4-dilithiocyclohexane and the like; and a combination of organolithium polyfunctional initiator with organomonolithium initiator.
• the copolymerization can be carried out by adding a polyfunctional monomer such as divinyl benzene, diisopropenyl benzene or the like to the organomonolithium initiator such as n-butyllithium, sec-butyllithium or the like before or during the copolymerization.
• a polyfunctional monomer such as divinyl benzene, diisopropenyl benzene or the like
• organomonolithium initiator such as n-butyllithium, sec-butyllithium or the like
• a polar compound such as a tertiary amine compound, an ether compound or the like is preferably used as a randomizing agent for the vinyl-substituted aromatic hydrocarbon.
• the feeding of monomers may be carried out by divisional charge or continuous increment for the formation of random copolymer.
• a halogenated tin compound is added to the copolymerization system.
• halogenated tin compound mention may be made of dimethyl dichlorotin, dibutyl dichlorotin, tin tetrachloride, tributyl chlorotin, butyl trichlorotin, methyl trichlorotin, tin dichloride and the like. Further, this halogenated tin compound may be used together with another coupling agent such as halogenated silicon compound, halogenated germanium compound, adipic acid diester or the like.
• the copolymerization is carried out with organolithium initiator containing not less than 50 mol % of organodilithium compound and then the coupling is carried out with a coupling agent containing at least 50 mol % of RR'SnX 2 or SnX 2 (wherein each of R and R' is an alkyl group, a cycloalkyl group, and aralkyl group or an aryl group, and X is a halogen atom), whereby the conjugated diolefinic copolymer containing at least a given amount of tin bonded to the copolymer and having an improved processability can be obtained.
• organolithium initiator containing not less than 50 mol % of organodilithium compound and then the coupling is carried out with a coupling agent containing at least 50 mol % of RR'SnX 2 or SnX 2 (wherein each of R and R' is an alkyl group, a cycloalkyl group,
• the rubber composition for use in tire according to the invention comprises not less then 20% by weight, preferably 30% by weight of the above conjugated diolefinic copolymer.
• the other diolefine rubber to be blended with this copolymer mention may be made of natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, ethylene-propylene-diene terpolymer rubber, halogenated ethylene-propylene-diene terpolymer rubber and the like.
• the amount of the conjugated diolefinic copolymer according to the invention is less than 20% by weight, the balance between the wet skid resistance and the rolling resistance becomes unsatisfactory.
• additives and vulcanizing agent usually used in rubber industry.
• additives there are carbon black, white carbon, calcium carbonate, extender oil such as aromatic oil, naphthene oil or paraffin oil, and so on.
• the polymerization was carried out by using 100 g of styrene, 400 g of butadiene, 0.1 g of divinylbenzene and 6 millimol of n-butyllithium as a polymerization initiator, to which was then added 3.8 millimol of dibutyl dichlorotin. After the addition of 2.5 g of di-t-butyl cresol, the resulting product was subjected to solvent-removing and drying in the usual manner. As a result of analysis on the resulting polymer, the contents of vinyl bond and bound styrene were 59% and 20%, respectively, and ML 1+4 100 ° C. was 65, and the tin content was 900 ppm.
• a rubber composition was prepared by using each of Polymers A-I according to the compounding recipe shown in the following Table 1, kneaded in a plastomill of 250 cc, and vulcanized at 145° C. for 30 minutes. The properties of the vulcanizate were evaluated to obtain results as shown in the following Table 2.
• the rolling resistance was measured by means of a Dunlop flexometer. The larger the measured value, the lower the rolling resistance.
• the rolling resistance and the wet skid resistance are well balanced without damaging the fracture properties and wear properties, which makes possible to provide rubber compositions having excellent rolling resistance and processability.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Polymerization Catalysts (AREA)

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Cited By (49)

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• 1984
  • 1984-06-01 JP JP59110870A patent/JPS60255838A/ja active Granted
• 1985
  • 1985-05-28 GB GB08513289A patent/GB2160207B/en not_active Expired
  • 1985-05-30 DE DE3519430A patent/DE3519430C2/de not_active Expired
  • 1985-05-31 FR FR858508257A patent/FR2565236B1/fr not_active Expired
• 1987
  • 1987-07-06 US US07/070,117 patent/US4742124A/en not_active Expired - Lifetime

Patent Citations (6)

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